Contract cancelation

On the 20th of August 2018 I took out a contract for two phones and I received an approval not even 5 hours later. I wanted to cancel the contract under the 7 days grace period for one of the phones(o e I have received as the other one is out of stock and is for my partner) because I saw that they have a better deal which they did not show on their booklet but online. Upon calling I spoke to an advisor who was more than willing to arrange a return and cancel the contract until I explained how I got the contract and why I wanted to cancel. Apparently their telephonic aftersales team and their stores do not have the same terms and conditions which I find strange. How can one company have different terms and conditions and why would I be charged up to 75% of the contract when I haven't even had the phone for that long and why is it that the store consultants are never open to fully disclosing or engaging with customers when the cancelation topic is brought up?